Electromagnetically controlled fuel injection arrangement for internal combustion engines



w. REICHARDT 3,515,104 ELECTROMAGNETICALLY CONTROLLED FUEL INJECTION June 2, 1970 ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Filed July 5 1968 FIG] . w LP wf A; .YQPLIOAH 11w 3 i 3,3 (vi wvw w 1 fl J y PIC INVENTOR Wolfgang REICHARDT y his ATTORNEY Int. (:1. Find 5/02 US. Cl. 12332 4 Claims ABSTRACT OF THE DISCLOSURE An electronic arrangement for controlling the injection of fuel into the cylinders of an internal combustion engine equipped with electromagnetically actuated valves. The valves are opened for admitting fuel into the cylinder by applying to the valve an electrical signal derived from a multivibrator circuit. The duration of the opening signal applied to the valve is, in turn, varied as a function of an operating characteristic of the engine. A signal emitter actuated for every rotation of the crankshaft of the engine transmits a signal to the multivibrator for initiating an unstable state of the multivibrator and thereby generating the signal to be applied to the fuel injection valves. An inhibiting switching circuit is connected between the signal emitter and the multivibrator for inhibiting transmission of signals to the multvibrator when the throttle of the engine is in its idling position and the prevailing engine speed exceeds the idling speed of the engine.

BACKGROUND OF THE INVENTION In the fuel injection arrangements of the species associated with the present invention, it is possible to introduce a precise amount of fuel into a cylinder of an internal combustion engine. It is possible to regulate the amount of fuel thus introduced into the cylinder as a function of the prevailing operating conditions of the engine. It is of special advantage, in accordance with the present invention, that the monostable control circuit used to establish the opening duration of the injection valves, may be made to respond rapidly to variations in the operating conditions. In practical operation, it has been found desirable to avoid undesired exhaust arrangements. Accordingly, a self-operating cut-off arrangement is provided in which fuel injection is inhibited when the throttle of the engine is in its idling position, and the engine is, at the same time, operating at a speed exceeding that corresponding to the idling speed. Such an operating condition or situation may prevail in a motor vehicle when the driving wheels of the vehicle are coupled to the engine, and the vehicle drives as a result of its inertia even though the engine is not being driven. Under these circumstances the engine operates as a brake.

It is an object of the present invention to provide a reliably operating cut-off or blocking arrangement which is simple in construction. In accordance with the resent invention, it is provided that the blocking arrangement include a monostable multivibrator switching circuit between a signal generator coupled to the engine and a control multivibrator controlling the fuel injection valves. Such a monostable multivibrator switching circuit can be designed and constructed in a simple manner. This switching circuit may be made to switch the control multivibrator so as to permit fuel injection under prescribed operating conditions. These conditions are that no fuel injection is to take place when the throttle is in its idling position and when the engine is rotating at a speed exceeding the speed associated with the idling condition of the engine.

United States Patent 0 The control multivibrator circuit determines through the period of its unstable state, the injection duration for the fuel injection valves.

In a preferred design, the monostable switching circuit ncludes a timing network having a capacitor and a switching transistor. The switching transistor is connected to the capacitor through its base, preferably by way of a diode. The transistor is also connected to an operating current source which returns the transistor to its stable operating state. This connection to the current source is made through a resistor. The circuit is also provided with a switch coupled to the throttle. The arrangement of the switch is such that in the idling position of the throttle the discharge of the capacitor is considerably delayed. Through this arrangement it is possible to achieve that the switching circuit transfers to its stable state at the desired engine speed exceeding considerably the idling speed. Under this set of conditions, the end of each resulting pulse is immediately followed by the beginning of the subsequent pulse without any interval inbetween. In this manner no actuating pulse can be transmitted at the output of the switching circuit and onto the control multivibrator connected thereto. The discharge time constant of the capacitor must be increased for the transition to the cut-oif state. This is accomplished in a particularly simple manner by connecting the capacitor to a discharge transistor. The conducting state of this transistor is influenced by the switch coupled to the throttle. The capacitor is preferably connected in series with the emittercollector path of the discharge transistor. A first diode and a first emitter resistor is also preferably connected in series with this emitter-collector path. The emitter resistor is connected to the switch actuated by the throttle.

In practical operation it has been found desirable to shift the engine speed to a higher value when the engine temperature decreases. This is under the condition that the cut-off arrangement is in the self-operating state. The discharge transistor is, furthermore, connected through its base to a tap of a voltage divider associated with an operating source. The emitter is also connected to the tap of a second voltage divider associated with the supply or source, by way of a second diode and a second emitter resistor. This second voltage divider includes a temperature sensitive resistor thermally coupled to the engine. In a further embodiment of the present invention it is also provided that the capacitor determining the unstable state of the switching circuit is discharged more slowly when the control multivibrator was not actuated and the engine speed drops. Under these conditions provision is included for reinstating the injection pulses at low engine speeds and to assure that the injection pulses are blocked or inhibited for the higher speeds. This provision resides in the configuration that a third diode and a third emitter resistor are connected in the emitter path of the discharge transistor. An auxiliary transistor is, furthermore, connected to the control multivibrator by way of a coupling capacitor. The auxiliary transistor is of the opposite type of the discharge transistor and is connected through its collector to the third diode and the third emitter resistor.

SUMMARY OF THE INVENTION An arrangement for controlling the injection of fuel into internal combustion engines. The fuel is passed to the cylinders of the engine through electromagnetic valves. Each cylinder is provided with one such electromagnetically operated valve. The electrical signal for opening the valve is derived from a monostable multivibrator circuit which provides the opening signal for the valve during the unstable state of the monostable circuit. The time interval of the signal from the multivibrator circuit is, in turn, varied as a function of an operating parameter of the engine such as, for example, the intake manifold pressure. The multivibrator circuit is actuated periodically through a switch mechanically operated by the crankshaft of the engine. The arrangement is such that for every rotation of the engine the switch transmits an electrical signal to the multivibrator circuit. An inhibiting switching circuit is connected between the mechanically operated switch and the multivibrator circuit. This inhibiting circuit inhibits the signals from reaching the multivibrator when the throttle of the engine is in its idling position and the speed of the engine exceeds the idling speed. Under these circumstances, the multivibrator circuit is not actuated and n fuel injection into the cylinders of the engine takes place.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a functional schematic diagram showing the engine with its cylinders and electromagnetically actuated valves which are controlled by signals derived from a multivibrator circuit actuated in a predetermined manner, in accordance with the present invention;

FIG. 2 is an electrical schematic diagram showing the electronic components and their interconnections for deriving the electrical signals for controlling the electromagnetically actuated valves for injecting fuel into the engine under predetermined conditions specified in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, the four-cylinder, four-- cycle internal combustion engine 1 is provided with an electromagnetically operated injection valve for each one of the individual cylinders. Each of these cylinders leads to the intake manifold 2 having branches communicating with the individual cylinders. Fuel is provided to the individual cylinders through the communicating lines 4 stemming from a distributing reservoir 5. The electromagnetically operated injection valves control the injection of fuel from the lines 4 into the cylinders. The fuel pressure within the reservoir 5 is maintained at substantially constant pressure by means of a pump 6. This pump 6 is driven by an electrical motor (not shown) which may be operated from the battery used in conjunction with the internal combustion engine for the motor vehicle.

The injection valves 3 permit fuel to be injected into the individual cylinders, by an amount proportional to the time duration during which the valves are open. These electromagnetically operated valves are controlled in operation by rectangular-shaped pulses. The pulses control the duration of the opening of the valves. A power transistor LT provides the opening-pulses for operation of the individual valves. The power transistor LT is made conductive or turned-on by means of a control arrangement described in detail below. The emitter of the transistor is connected to the positive terminal of the battery used in conjunction with the engine, whereas the collector of the transistor is connected to the common junction of the resistors designated to represent the electromagnetic coil-s of the valves. When the power transistor LT is turned on, current flows through the emitter-collector path of the transistor, and thus provides current flow to the electromagnetically controlled valves.

The electrical control arrangement for controlling the power transistor LT includes a monostable multivibrator circuit C for determining the opening duration of the injection valves. The timing interval associated with the multivibrator circuit C is made dependent upon the variable pressure within the intake manifold 2, through the use of a pressure or vacuum sensing device 8. The latter may be designed to operate, for example, on the basis of a mechanical diaphragm which is displaced as a function of the absolute pressure applied to it on the sides of the diaphragm.

The control multivibrator circuit C includes, in particular, an input transistor 60 andan output transistor 70, both of the pup type. The emitters of these two transistors are both connected to the circuit path M leading to the negative terminal of the battery (not shown) for operating the ignition arrangement of the internal combustion engine. In the feedback branch between the collector of the output transistor 70 and the base of the input transistor 60, a transformer 71 is provided. The latter has a ferromagnetic core 75 which may be displaced for varying the inductance linking the coils of the transformer. The ferromagnetic core 75 is mechanically linked with the pressure sensing device 8 by means of the dash-dot-dash-pot lines shown in the drawing. As a result of this combination, the inductance of the transformer is varied as a function of the prevailing manifold pressure. With this variation in the inductance, a corresponding variation in the unstable period of the monostable multivibrator circuit is realized. This varying timing of the monostable multivibrator circuit, therefore establishes the injection period of the fuel as a function of the intake manifold pressure. In order to maintain the input transistor 60 conductive during its quiescent state, the base of the transistor leads to the positive terminal P of the battery, by way of a diode 62 and a resistor 63. The diode 62 is connected in the circuit such that its cathode is connected to the base of the transistor 60, whereas its anode is connected to the resistor 63. The base of the output transistor 70 leads to the negative terminal of the battery M, by way of the resistor 67. At the same time, the base also leads to the collector of the transistor 60, via the resistor 66. The junction at which the collector of transistor 67 is connected to the resistor 66, leads to the positive terminal of the voltage supply P, by way of the resistor 65. The output transistor 70 can only be made conductive when the input transistor 60 is first cut off through a signal 78 applied to the junction 68 in FIG. 2. When the resistor 70 is thus made conductive or is turned on, current flows through the emitter-collector path of the transistor and therefore also through the primary winding 76 of the transformer. This current flow associated with the output transistor 70* also is efiective in turning on the transistor LT so that the latter is made conductive. At the same time, this action of the output transistor 70 resulting in current flow through the primary winding 76, also induces a cut-off voltage in the secondary winding 77. This cut-off voltage signal is applied to the base of the input transistor 60 .by way of the diode 64. The cut-off state and the following unstable state of the monostable multivibrator circuit C prevails until the exponentially rising current through the primary winding 76 attains its maximum value. Upon that condition, the induced voltage in the secondary winding becomes insufficient to maintain the input transistor 60 cut off. The control multivibrator circuit, as a result, returns to its original stable operating state until the next cycle.

The monostable multivibrator circuit C is actuated by the signal generator S for every rotation of the crank shaft. The signal generator S comprises essentially a switch 10 operated by a cam actuating segment N. The cam is, in turn, mechanically linked to the crankshaft of the engine by means of the linkage 7 schematically represented by dash-dot lines. The operation of the switch 10 is thus made synchronous with the rotation of the crankshaft such that the switch is, for example, closed once for every revolution of the crankshaft. In accordance with FIG. 2, the movable switching arm of the switch 10, is connected to a resistor 22 leading to the positive terminal P of the voltage supply. The switching arm is also connected to the capacitor 23 having its other terminal joined to a diode 24 and a resistor 29. The path through the diode 24 leads to the negative voltage supply terminal M, whereas the path through the resistor 29 leads to the positive voltage supply terminal P. As long as the switching arm 10 is in its open position, the capacitor 23 can have one of its electrodes charged positive through the resistor 22, while the other electrode is charged negative through the junction 28. If, now, the junction 28 were connected to the junction 68, as in the commonly known arrangements, the monostable multivibrator circuit C would be actuated to its unstable state at every revolution of the crankshaft, without taking into account the other prevailing operating parameters. As a result, an injection pulse would be generated at every revolution of the crankshaft, independent of the various prevailing operating parameters.

For reasons indicated supra, fuel injection to the internal combustion engine should be out 01f when the following three conditions prevail simultaneously:

(a) throttle is in the idling position,

(b) the rotational speed exceeds a predetermined minimum value, as for example, 2,000 rpm, and

(c) the operating temperature of the internal combustion engine exceeds a minimum value of, for example, 60 C.

A monostable switching circuit A is arranged between the signal generator S and the monostable multivibrator C for determining the duration of injection. The circuit A inhibits any transmission of signals from the signal generator S to the control multivibrator C, when the three conditions above prevail.

The monostable switching circuit A consists essentially of a timing network having a capacitor 31 in which one of its two electrodes is connected directly to the negative voltage supply terminal M. The other electrode of the capacitor 31 leads to the capacitor 23, by way of the diode 25. The anode of the latter is connected to the capacitor 31. This other electrode of the capacitor 31 is also connected to a diode 42 through the junction 39. The diode 42 leads to the base of a switching transistor 40 within the circuit A. The transistor 40 conducts while in the quiescent state, since it is provided with suflicient base current through the series circuit of the diode 42 and resistor 43 leading to the positive voltage supply terminal P. The transistor 40 is of the pnp type, and is cut off for each closure of the switching arm 10, provided the three operating conditions enumerated above do not prevail simultaneously. As a result, the phase inversion transistor 50 is made conductive by having its base connected to the collector of the transistor 40 and the resistor 44. Through the provision of the coupling capacitor 52 connected to the collector of the transistor 50, the actuating signal 78 is applied to the transistor 60, by way of the diode 57.

An idling switch 38 is provided for purposes of producing the desired cut-01f while in the idling position of the throttle 9 denoted by dashed lines and simultaneously exceeding the predetermined minimum value n =2,000 rpm. for the rotational speed n. The throttle 9 is mechanically linked to the gas pedal G. The idling switch 38 is associated with the switching circuit A. The switch 38 is also mechanically actuated by the gas pedal G. This mechanical linkage between the switch 38 and the gas pedal G is denoted by the dash-dot line in FIG. 1. The circuit for the idling switch 38 is arranged such that when the switch closes, corresponding to the idling position of the throttle 9, the discharge of the capacitor 31 is extremely delayed. The capacitor 31 is connected to a discharge transistor 30 which is influenced by the switch 38 by being 6 connected to the switch through the diode 36 and the emitter resistor 37. Thus, the switch 38 is connected to the junction of the resistor 37 leading to the positive voltage supply terminal, as well as the anode of the diode 36.

Aside from the prevailing position of the idling switch 38, a second and a third parameter may influence the discharge transistor 30. The second parameter for influencing the discharge transistor 30 is designated as the operating temperature of the internal combustion engine. The temperature is taken into account by providing a temperature sensitive resistor 20 in series with a fixed resistor 21. The junction 12 between the two resistors functions as a voltage divider, and is applied to a resistor 33. The latter is in turn connected in series with a diode 32 leading to the emitter of the transistor 30. The base of the transistor 30 is itself connected to a voltage divider consisting of the resistors 26 and 27.

The switching state of the circuit A operates as the third parameter for influencing the conducting state of the transistor 30. This is accomplished by providing an auxiliary timing stage Z connected to the control multivibrator circuit C. The timing stage Z includes a transistor of the pnp type. This transistor is conductive in its quiescent state since it obtains base current through the series circuit including the diode 82 and the resistor 83 leading to the positive voltage supply terminal P. The transistor 80 has its base connected, by way of the diode 82, to the collector of the transistor 60. This connection is made through the coupling capacitor 73, and as a result, the timing stage Z is actuated each time that the control multivibrator C is actuated. The capacitor 73 can only become charged when the monostable control multivibrator circuit C is in its unstable state. In this unstable state of the circuit C the input transistor 60 is cutoff, and therefore the capacitor 73 may obtain charging current through the collector resistor 65. As soon as the control multivibrator circuit C attains the terminal instant of its opening pulse and returns to its stable operating state, the input transistor is made again conductive. At this very instant the charge upon the capacitor 73 cuts ofi the transistor 80 for a short period of time which is determined by the magnitude of the capacitor 73 and the resistor 83 which establishes the timing network of the RC network.

In the operation of the circuit of FIG. 2, the capacitor 23 has one of its electrodes connected to the negative voltage supply terminal M, as soon as the switch 10 is closed. As a result, a negative step voltage is applied to the junction 28. This step voltage is of the magnitude corresponding to the battery voltage. The diode 24 closes and the diode 25 opens and, accordingly, the negative step signal appears also at the junction 39. An interchange of charge takes place between the capacitors 23 and 31, by

way of the diode 25. This interchange of charge between.

the two capacitors takes place relatively rapidly. The capacitor 23 discharges very rapidly through the resistor 29, and this manner no longer aifects the pulse duration of the monostable multivibrator after the charging interchange. The capacitor 31 discharges through the resistor 43 and the transistor 30. The negative step voltage at the junction 39 cuts off the diode 42 and interrupts thereby the base current to the transistor 40. As a result, the transistor 40 becomes cut OE and the transistor 50 is again made conductive. The negative voltage step at the collector of the transistor 50 is transmitted to the junction 68 by way of the capacitor 52 and the diode 57. The capacitor 52 in combination with the resistors 53 and 54 forms a differentiating network. The negative step voltage at the collector of the transistor-50, therefore, results in an actuating pulse 78' at the junction 68. The diode 62 becomes cut off and interrupts the base current to the transistor 60, so that the latter becomes cut oif. The transistor 70 now becomes conductive and the rising current in the transmission circuit 71 is applied to the junction 68 by way of the secondary winding and the diode 64. This current rise maintains the transistor 60 out ofi even after the 7 actuating pulse ceases. The capacitor 73 is charged by way of the resistor 65, the diode 82 and the base-emitter path of the transistor 80.

When the current rise in the transmission circuit 71 is terminated, the control multivibrator returns to its stable state. The inductance of the transmission circuit 71 is made dependent upon the intake manifold pressure in the well known manner. As a result of this state of the control multivibrator, the transistor 60 is made conductive and the negative voltage step at its collector, cuts off the diode 82 through the path of the capacitor 73. In this manner, the transistor 80 is also cut off until the capacitor 73 has discharged through the resistor 83.

The transistor 40 still remains cut-off. When the internal combustion engine is at its operating temperature, the temperature sensitive resistor 20 has a low ohmic or resistance value, and as a result the diode 32 is cut off. In this manner, no discharge current of the capacitor 31 can flow through the resistor 33. The switch 38 is closed, and by being coupled or linked to the throttle 9, it indicates that the throttle is in its idling position. No discharge current can therefore also flow from the capacitor 31 through the resistor 37, since the diode 36 is biassed in the cut-off direction.

As long as the transistor 60 conducts the diode 34 is biassed in the cut-off direction, and a discharge current of the capacitor 31 flows through the resistor 35. If the transistor 80 is cut off after a predetermined interval upon the termination of a pulse from the control multivibrator C, current can flow through the resistor 35, the diode 34, and the transistor 30. During this cut-off period of the transistor 80, the capacitor 31 becomes discharged more rapidly.

If the capacitor 31 is discharged after a period of time determined by the conducting state of the discharge transistor 30, then the transistor 40 becomes again conducting and the transistor 50 is cut off. The switch then becomes again opened and the capacitor 23 becomes charged. The initial state of the arrangement is thus again realized.

In contrast to this, the fuel flow tothe loaded internal combustion engine is interrupted in the following manner when the switching arm 10 closes for providing an opening pulse to the injection valves.

Assume that the rotational speed of the internal combustion engine is so high, that the transistor 40 remains cut off as a result of the charge on the capacitor 31, when the switch 10 doses again. Under these conditions an interchange of charge occurs between capacitors 23 and 31, without the transistor 40 becoming conductive. Therefore, upon closure of the switch 10, no negative pulse is applied to the collector of the transistor 50 which remains cut-off. The control multivibrator C is also not actuated. As a result, the timing stage Z is not actuated and no discharge current of the capacitor 31 flows through the transistor 30. At the same time, the pulse duration of the monostable circuit A becomes larger. Through these conditions, a hysteresis effect arises when the rotational speed is reduced. The control multivibrator can thus first be actuated againat a lower rotational speed.

When the internal combustion engine is cold, the resistance value of the resistor increases since the latter is designed to be temperature-dependent and in the form or a thermal conductor. The voltage at the junction 12 of the voltage divider becomes more positive. When a predetermined threshold value has been attained, the diode 32 conducts and a portion of the discharge current of the capacitor 31 flows through the transistor 30, the diode 32, and the resistors 33 and 21. The pulse duration of the multivibrator is thereby reduced and the rotational speed at which cut ofl? takes place is shifted to a higher value. The same situation applies to the re-initiating rotational speed.

The fuel flow is to be interrupted only when the throttle 9 is closed. If this is not the case, then the switch 38 is opened and as a result, the discharge current of the capacitor 31 becomes increased through the resistor 37. The unstable switching period of the circuit A is thereby reduced to the extent that cut-off is first realized at a rotational speed which is, for example, above the allowable maximum speed of the engine by a factor of 2.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of fuel injection arrangement for internal combustion engines.

While the invention has been illustrated and described as embodied in a fuel injection arrangement for internal combustion engines, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptatons should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. A fuel injection arrangement for an internal combustion engine comprising in combination, at least one electromagnetically operated injection valve controlling the flow of fuel to said engine through an electrical signal applied to said valve; a monostable control multivibrator circuit connected to said injection valve and applying said electrical signal to said valve, said electrical signal occurring during the unstable state of said control multivibrator and having a duration dependent upon the time interval of said unstable state; multivibrator adjusting means coupled to said engine and connected to said control multivibrator for varying said time interval of said unstable state of said control multivibrator as a function of an operating parameter of said engine; signal emitter means actuated by said engine and emitting an electrical signal for transmission to said control multivibrator to initiate the unstable state thereof; signal inhibiting means connected between said signal emitter means and said control multivibrator for inhibiting transmission of the signal from said signal emitter to said control multivibrator when the throttle of the engine is in the engine idling position and the prevailing engine speed exceeds the idling engine speed, said sign-a1 inhibiting means comprising further: a monostable switching circuit with capacitor and switching transistor interconnected as a timing network; rectifier means connected to said capacitor and the base of said switching transistor; a source of voltage supply; a resistor connected between said source of voltage supply and the junction of said capacitor and said rectifier; switching means actuated by the throttle of said engine and delaying the discharge of said capacitor when said throttle is in its idling position; a discharge transistor connected to said capacitor and having a conducting state determined by the action of said switching means coupled to said throttle of the engine; a first diode connected in series With the emittercollector path of said discharge transistor; and a first emitter resistor connected in series with said first diode, said switching means actuated by said throttle being connected to the junction of said first diode and said first emitter resistor. J

2. The fuel injection arrangement for an internal combustion engine as defined in claim 1 including a first voltage divider having a voltage tap connected to the base of said discharge transistor; a second diode connected to the emitter-collector path of said discharge transistor; a second emitter resistor connected in series with said second diode; a second voltage divider with voltage tap connected to said second emitter resistor; and a temperature sensitive resistor in said second voltage divider for varying the potential of said voltage tap of said second voltage divider as a function of the temperature of said internal combustion engine.

3. The fuel injection arrangement for an internal combustion engine as defined in claim 2 including a third diode connected to the emitter-collector path of said discharge transistor; a third emitter resistor connected in series with said third diode; an auxiliary transistor opposite in conductivty type from said discharge transistor, the collector of said auxiliary transistor being connected to the junction of said third diode and said third emitter resistor; and coupling capacitor means connected between said auxiliary transistor and said control multivibrator circuit.

4. The fuel injection arrangement for an internal combustion engine as defined in claim 3 including a fourth diode connected between said coupling capacitor and the base of said auxiliary transistor.

References Cited LAURENCE M. GOODRIDGE, Primary Examiner U.S. Cl. X.R. 123-139, 140 

